EP3700710B1 - Tensioning device and handheld machine tool - Google Patents

Description

The present invention relates to a clamping device for the axial clamping of a tool disk on a flange assigned to a drive spindle of a hand-held power tool. The clamping device has a screw which, in order to clamp the tool disk, is to be screwed into an internal thread of the drive spindle.

Such clamping devices are basically known from the prior art. Also known from the prior art are clamping devices with a clamping nut, in particular designed as a two-hole nut, which is to be fastened to the drive spindle with a corresponding tool. However, the present invention relates to a different class of clamping devices, namely those that have a screw that is to be screwed into an end internal thread of the drive spindle.

For example, in the EP 3 202 533 A1 discloses a clamping device for axially clamping a disk-shaped tool, which tool may preferably be a cutting disk. The clamping device EP 3 202 533 A1 comprises a first and a second securing element, the first securing element of the tensioning device being rotatably mounted relative to a screw and non-rotatably relative to the tensioning disk.

It is the object of the present invention to provide a clamping device which counteracts the clamping device releasing itself—and thus counteracting the tool disk becoming loose during operation of the hand-held power tool.

The object is achieved in that the screw is mounted in a coupling module of the clamping device, the coupling module having an inner contour which is paired or can be paired with the drive spindle in a form-fitting, non-rotatable manner in the circumferential direction, the screw being mounted in the coupling module via a roller bearing, the roller bearing being designed as an angular ball bearing.

The clamping device according to the invention has the advantage that it can neither be tightened nor loosened during operation of the hand-held power tool because the coupling module, as part of the clamping device, is paired with the drive spindle in a form-fitting, non-rotatable manner. This as a counterpart to a flange that is preferably paired with the drive spindle in a form-fitting, non-rotatable manner.

It has proven to be advantageous if the inner contour of the coupling module is designed as a hexagonal profile. A corresponding outer contour of the drive spindle is preferably designed as an external hexagon. Alternative form-fitting non-rotating pairings, for example in terms of a form-fitting shaft-hub connection, can be used.

The internal thread of the drive spindle is preferably an end internal thread. The internal thread can be set back in the axial direction in relation to a top surface of the drive spindle. The screw preferably protrudes in the axial direction beyond the coupling module, in particular opposite the cylindrical section of the coupling module. The coupling module is preferably of cylindrical design. Preferably, the coupling module has a cylindrical section that can protrude through a central opening of the tool disk. The cylindrical section of the coupling module can protrude into a central opening of the flange.

In a preferred embodiment, the tensioning device has a hand knob which is formed in a form-fitting, non-rotatable manner with the screw in the circumferential direction. As a result, the clamping device can be handled particularly easily. An additional assembly tool, such as an assembly wrench, can be dispensed with.

In a particularly preferred embodiment, the clamping device has a clamping element, which can be subjected to an axial clamping force by means of the coupling module, in order to clamp the tool disk against the flange in this way. The clamping element is particularly preferably designed as a spring steel sheet. The spring plate can be disc-shaped. According to the invention, it is provided that the screw is mounted in the coupling module via a roller bearing. Because head friction of the clamping element can be reduced with the aid of the roller bearing, an increased clamping force of the clamping device is achieved.

The roller bearing is designed as an angular contact ball bearing. The angular contact ball bearing preferably has a contact angle between 35° and 45°. The contact angle can be 40°. Due to the diagonal contact angle of the rolling elements, especially in an angular contact ball bearing, the clamping device wedges radially towards the end of the clamping process. This provides increased security against accidental loosening.

If the clamping device has a clamping element in the form of a spring plate, which is preferred, the clamping device has increased insensitivity to settlement, since the spring plate is in frictional contact with the tool disk, which compensates for thermal expansion.

In a further embodiment, the tensioning device has an elastomer ring, which is preferably arranged between a head of the screw and a collar of the coupling module. Alternatively or additionally, the clamping device can have a retaining ring, by means of which the coupling module is held on the screw.

According to an advantageous embodiment of the present invention, a plate spring can also be provided instead of an elastomer ring. The disc spring can serve to to seal a grease space between the screw head and the collar of the coupling mode. In addition, the disk spring can also pretension the hand knob axially.

According to a further advantageous embodiment, it is also possible for a combination of an elastomer element and a mechanical spring to be used instead of the elastomer ring.

It has proven to be advantageous if the tensioning element is held on the coupling module by means of a retaining ring.

In a further preferred embodiment, the tensioning device has a stop, via which a deflection of the tensioning member is directly or indirectly limited. The stop is preferably designed as an annular collar and is arranged between the spring plate and the tool disk to be accommodated. If the tool disk comes into contact with the stop during the clamping process, a deflection of the spring element in the axial direction is limited.

The object is also achieved by a hand-held power tool, preferably in the form of a grinder or cut-off grinder, with a drive spindle, which preferably has an internal thread at the end, and with a clamping device of the type described above. The drive spindle has an outer contour which is paired or can be paired with the inner contour of the coupling module in a form-fitting, non-rotatable manner in the circumferential direction.

It has proven to be advantageous if the hand-held power tool comprises a flange which is or can be connected to the drive spindle in a form-fitting, non-rotatable manner by means of an anti-rotation device in the circumferential direction.

The handheld power tool according to the invention can be advantageously further developed in a corresponding manner by the features explained with reference to the clamping device.

Further advantages result from the following description of the figures. Various exemplary embodiments of the present invention are shown in the figures. The figures, the description and the claims contain numerous features in combination.

In the figures, the same and similar components are denoted by the same reference symbols.

• Fig. 1 ein bevorzugtes Ausführungsbeispiel einer erfindungsgemäßen Spannvorrichtung zusammen mit einer Werkzeugscheibe und einer Handwerkzeugmaschine;
• Fig. 2 die Spannvorrichtung der Fig. 1 in Vorder- und Rückansicht;
• Fig. 3 die Spannvorrichtung der Figuren 1 und 2 in Explosionsdarstellung;
• Fig. 4 die Spannvorrichtung der vorgehenden Figuren in Schnittdarstellung;
• Fig. 5 ein zweites Ausführungsbeispiel einer erfindungsgemäßen Spannvorrichtung im Teilschnitt; und
• Fig. 5a ein drittes Ausführungsbeispiel einer erfindungsgemäßen Spannvorrichtung im Teilschnitt.

Show it:

• 1 a preferred embodiment of a clamping device according to the invention together with a tool disc and a hand tool;
• 2 the clamping device 1 in front and rear view;
• 3 the clamping device figures 1 and 2 in exploded view;
• 4 the clamping device of the preceding figures in a sectional view;
• figure 5 a second embodiment of a clamping device according to the invention in partial section; and
• Figure 5a a third embodiment of a clamping device according to the invention in partial section.

Examples:

A preferred embodiment of a clamping device 10 according to the invention is shown in 1 shown. The clamping device 10 serves to clamp a tool disk 300 in the axial direction AR. The tool disk 300 is to be braced between the clamping device 10 and a flange 30 , the flange 30 being associated with a drive spindle 20 of a hand-held power tool 100 .

The flange 30 has an anti-twist device 24 in the form of a lateral recess, so that the flange placed on the drive spindle 20 is positively connected to the drive spindle 20 in the circumferential direction U so that it cannot be twisted.

Again 1 can be removed, the clamping device 10 has a screw 2 which is to be screwed into an end internal thread 22 of the drive spindle 20 in order to clamp the tool disk 300 . On the underside of the clamping device 10, a coupling module 1 of the clamping device 10 provided according to the invention can already be seen to some extent, in which the screw 2 is centrally mounted. The inner contour of the invention is later with reference to 2 explained in more detail.

Again 1 can be removed, the clamping device 10 has a hand knob 3 . This is used for manually screwing the screw 2 into the internal thread 22 and thus for axially clamping the tool disk 300 between the clamping device 10 and the flange 30. For this purpose, a head of the screw 12 has an outer hexagonal contour, for example, which is embedded in a corresponding inner hexagonal contour of the hand knob 3 . However, almost any other suitable contour can also be used as an alternative to the hexagonal contour.

Again 1 can be seen below, the drive spindle 20 has an outer contour, which is present, for example, designed as a hexagonal profile. An inner contour of the coupling module 1 (not shown here) can be paired with a positive fit to this outer contour 26. A form-fitting, twist-proof pairing between the coupling module 1 and the outer contour 26 is achieved when the clamping device 10 is clamped, with the coupling module 1 protruding at least in sections through a central opening 301 of the tool disk 300.

2 now shows the clamping device 10 of 1 in top view ( Figure 2A ) as well as in bottom view ( Figure 2B ).

Good to see in Figure 2A is the hand knob 3 already described, in which the screw 2 is embedded by means of its head 12 in a form-fitting, non-rotatable manner in the circumferential direction. The tensioning device 10 also has a tensioning element, which is designed here, for example, in the form of a plate-shaped spring plate 4 . The actual clamping force is applied to the tool disk 300 by means of the spring plate 4 .

In Figure 2B the central screw 2 of the clamping device 10 is clearly visible. The screw is mounted in the coupling module 1 of the clamping device 10, more precisely, the screw 2 is mounted coaxially in the coupling module 1. A cylindrical section 13 of the coupling module 1 is clearly visible, with the cylindrical section 13 protruding at least in sections through the central opening 301 of the tool disk 300 when the tool disk 300 is clamped (cf. 1 ) runs.

According to the invention, the coupling module 1 has an inner contour 16 which, in the circumferential direction U, is positively locked against rotation with the drive spindle 20 (cf. 1 ) can be paired. According to the preferred embodiment shown, the inner contour 16 is designed as a hexagonal profile.

3 now shows the preferred embodiment of the clamping device 10 of the previous figures in an exploded view. In the upper area of the 3 the screw 2 can be seen with its screw head 12 which, for example, has an external hexagonal contour. A thread 14 of the screw 2 can be seen in the lower area, which turns into an internal thread (cf. 1 : internal thread 22) is to be screwed in. The screw 2 is mounted in the coupling module 1 via a roller bearing, preferably an angular contact ball bearing 5 .

An elastomer ring 6 shown below the hand knob 3 serves, among other things, to hold the outer contour of the screw head 12 within a corresponding inner contour of the hand knob 3. This is evident in particular from FIG 4 apparent. The coupling module 1 can be seen below the elastomer ring 6, which in addition to the already described cylindrical section 13 and the hexagonal inner contour 16 also has a collar 11. The collar 11 is designed and provided to transmit a clamping force applied via the hand knob 3 and the screw 2 to the spring plate 4 .

In the circumferential direction U, the coupling module 1 can be paired with the spring plate 4 in a form-fitting, non-rotatable manner, in the assembled state. This preferably applies to all exemplary embodiments. For this purpose, the coupling module 1 has a module contour 19 below the collar 11 of the coupling module 1 , which corresponds to an inner contour of the spring plate 4 . For example, the module contour 19 is designed as an external square. A retaining ring 7 by means of which the coupling module 1 is held on the screw 2 can be seen below the coupling module 1 .

The clamping element, here in the form of the spring plate 4, is held on the coupling module 1 by means of a retaining ring 8. The function of the clamping device 10 according to the invention is now with reference to 4 be explained in more detail.

First, if necessary, the flange 30 (cf. 1 ) is plugged onto the drive spindle 20 of the hand-held power tool 100 . The anti-twist device 24 connects the flange 30 in the circumferential direction U in a form-fitting, non-twistable manner to the drive spindle 20 . Then the cutting wheel 300 is inserted. When the clamping element 10 is applied, the inner contour 16 (here a hexagon socket) first comes into positive contact with the outer contour 26 of the drive spindle 20 non-rotating engagement. This is preferably done before the thread 14 of the screw 2 enters the internal thread 22 of the drive spindle 20 .

When screwing in the clamping device 10, manual force is transmitted to the screw 2 via an operating element, which is designed as a hand knob 3, for example. This is because the head 12 of the screw 2 is embedded in the circumferential direction in a form-fitting, non-rotatable manner in the hand knob 3 . At the latest when the spring plate 4 rests on the tool disk 300, the head 12 of the screw 2 slides over the angular contact ball bearing 5 relative to the coupling module 1 until at the end of the spring deflection of the spring plate 4 a radial tension prevails. As a result, there is both an axial and a radial tension between the head 12 of the screw 2 and the coupling module 1, with the radial tension in particular producing the higher holding effect. The radial tension is achieved in that the roller bearing that is preferably provided is designed as an angular contact ball bearing 5, which, for example, has a contact angle BW of 40° (cf. also figure 5 ) having. This increases head friction on the screw head 2, which prevents the clamping device 10 from being released unintentionally.

The elastomer ring 6 located between the coupling module 1 and the head 12 of the screw 2 presses on the one hand a section of the knob 3 against the screw head 12 and thus serves to prevent lubricant from escaping from the rolling body space. On the other hand, the elastomer ring 6, in cooperation with the retaining ring 7, holds the coupling module 1 on the screw 2. A locking ring 8 shown below the spring plate 4 serves to hold the clamping plate 4 on the coupling module 1.

Again 4 can be removed, the clamping force is transmitted in the axial direction AR via a collar 11 of the coupling module 1 to the spring plate 4 and from there to the tool disk 300 . Relative to the circumferential direction U, the spring plate 4 and the coupling module 1 are coupled to one another in a form-fitting, non-rotatable manner.

figure 5 Finally, FIG. 1 shows another preferred exemplary embodiment of a clamping device 10 according to the invention. Here, too, a roller bearing in the form of an angular contact ball bearing 5 is provided between coupling module 1 and screw 2, which has a contact angle BW of 40° (example). Unlike the one related to 4 described embodiment, the embodiment of figure 5 a stop 9, via which a deflection of the clamping member, which is designed here as a spring plate 4, can be limited.

In Figure 5a Another preferred embodiment of a clamping device 10 according to the invention is shown. Here, too, a roller bearing in the form of an angular contact ball bearing 5 is provided between the coupling module 1 and the screw 2, which has a contact angle BW of 40° (example). Unlike the one related to 4 described embodiment is provided instead of the elastomer ring 6 for sealing and preloading of the hand knob 3, a plate spring 6a. Again Figure 5a can be seen, the disc spring 6a is between a bottom of the hand knob 3 and a top of the collar of the coupling module 1 1 positioned so that the spring force of the cup spring 6a acts on the underside of the hand knob 3 and the top of the collar of the coupling module 11. The plate spring 6a positioned in this way serves, among other things, to hold the outer contour of the screw head 12 within a corresponding inner contour of the hand knob 3.

Reference List

1

coupling module

2

screw

3

hand knob

4

spring plate

5

Angular ball bearing

6

elastomer ring

6a

disc spring

7

retaining ring

8th

locking ring

9

attack

10

clamping device

11

collar of the coupling module

12

head of the screw

13

cylindrical section

14

thread

16

inner contour

19

module contour

20

drive spindle

22

inner thread

24

anti-rotation device

26

outer contour

30

flange

100

hand tool

300

tool disc

301

central passage opening

AR

axial direction

BW

contact angle

u

circumferential direction

Claims (10)

1. Clamping device (10) for the axial (AR) clamping of a tool disk (300) on a flange (30) associated with a drive spindle (20) of a hand-held power tool (100), wherein the clamping device (10) has a screw (2), which is to be screwed into an internal thread (22) of the drive spindle (20) to securely clamp the tool disk (300),
   characterized in that
   the screw (2) is mounted in a coupling module (1) of the clamping device (10), wherein the coupling module (1) has an internal contour (16) which is paired or can be paired positively with the drive spindle (20) for conjoint rotation in the circumferential direction (UR), wherein the screw (2) is mounted in the coupling module (1) by means of a rolling bearing, wherein the rolling bearing is designed as an angular contact ball bearing (5).
2. Clamping device (10) according to Claim 1,
   characterized in that
   the clamping device (10) has a knob (3), which is designed to be positively locked to the screw (2) for conjoint rotation in the circumferential direction (U).
3. Clamping device (10) according to Claim 1 or 2,
   characterized in that
   the clamping device (10) has a clamping member, preferably in the form of a spring plate (4), which can be subjected to an axial clamping force by means of the coupling module (1) in order in this way to clamp the tool disk (300) against the flange (30).
4. Clamping device (10) according to Claim 1,
   characterized in that
   the angular contact ball bearing preferably has a contact angle (BW) of between 35 degrees and 45 degrees.
5. Clamping device (10) according to any one of the preceding claims,
   characterized in that
   the clamping device (10) has an elastomer ring (6), which is preferably arranged between a head (2') of the screw (2) and a collar (11) of the coupling module (1).
6. Clamping device (10) according to Claim 5,
   characterized in that
   the clamping device (10) has a holding ring (7), by means of which the coupling module (1) is held on the screw (2).
7. Clamping device (10) according to any one of Claims 3 to 6,
   characterized in that
   the clamping member is held on the coupling module (1) by means of a retaining ring (8).
8. Clamping device (10) according to any one of Claims 3 to 7,
   characterized in that
   the clamping device (10) has a stop (9), by means of which a deflection of the clamping member is limited directly or indirectly.
9. Hand-held power tool (100), preferably in the form of a cutoff grinder, having a drive spindle (20), which has an internal thread (22) at the end, and having a clamping device according to any one of the preceding claims, wherein the drive spindle (20) has an external contour (26) which is paired positively with the internal contour (16) of the coupling module (1) for conjoint rotation in the circumferential direction (U).
10. Hand-held power tool (100) according to Claim 9, comprising the flange (30), which is connected or can be connected positively to the drive spindle (20) for conjoint rotation in the circumferential direction (U) by means of an anti-rotation safeguard (24).

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